Ultrastructure of meningiomas: autophagy is involved in the pathogenesis of "intranuclear vacuoles"

We report here common ultrastructural findings in a short list of meningiomas. At the lower power magnification, a tumour consisted of elongated or round cells and innumerable cellular processes connected with diverse intercellular junctions. Nuclei presented no specific features, nucleoli were infrequently seen and heterochromatin was clumped beneath the nuclear membranes. In a case of clear cell meningioma, cells were of watery cytoplasm. Occasionally, immobile cilia, completely ensheathed by the cytoplasm and anchored by blepharoplasts were seen; as we did not encounter those rare cilia in cross-sections, no further insight into their inner microtubular-doublet structure was possible. The cytoplasm of the cells and the processes were filled with the intermediate filaments. In the intercellular space, collagen fibrils and electron-dense material was occasionally observed. The majority of the tumour samples were filled with processes. Several types of junctional complexes were observed. The most frequent were desmosomes and in the proper plane of section their whole pentalaminar structure was readily discernible. However, robust tonofilaments, as seen in epithelial neoplasms, were not observed. Those desmosomal junctions were either completely symmetric or asymmetric, but the exact symmetry could not be judged without the assistance of a goniometer. Some junctional complexes were more elaborate, with desmosomal junctions separated by a tight apposition of membranes, which suggests tight junctions. "Intranuclear vacuoles" well-visible even at low power were defined as indentation of the cytoplasm into the nucleus. Within these vacuoles, autophagic vacuoles and lysosomal bodies were seen, suggesting an active macroautophagy process. In 2 cases, severe lipidization of meningioma cell cytoplasm was observed. In a case of anaplastic meningioma, a mitotic figure was found. In another case, empty rectangular spaces in the cytoplasm, suggestive of pre-existing crystalloid structures, were seen.

[Extracranial meningioma: morphological and histogenetical aspects and relations with perineurioma]

The clinicomorphological, immunohistochemical, and ultrastructural characteristics of 11 cases of extracranial meningioma versus 79 soft tissue perineuriomas were studied. There were significant similarities (cell morphology, immunoprofile, ultrastructural features of perineurial differentiation) of both entities. Considering the point of view that arachnoid and perineurial cells are anatomically, embryologically, and functionally related, it is most possible that extracranial meningiomas may be derived from perineurial cells (or their progenitor cell) rather than from displaced arachnoid cells.

An Ultrastructural and Immunohistochemical Study of Microcystic Meningioma with Emphasis on Matrix Proteins and Connexin 26 Type Gap Junctions

Although the histopathological subtypes of meningioma do not themselves appear to have prognostic significance, they are collectively important for defining the overall histopathological entity of microcystic meningioma (MCM) and allowing a distinction from other intracranial tumors, such as capillary hemangioblastoma, glioma, and metastatic renal cell carcinoma showing similar histology. Four cases of MCM were analyzed by conventional histology, immunohistochemistry, and electron microscopy. The present series of MCM was characterized by spindle- or cobweb-shaped tumor cells, characteristically associated small blood vessels, and a peculiar microcystic pattern. Among the microcystic meningeal tumor tissue, small areas of conventional subtypes were identified. Immunohistochemically, tumor cells showed the mesenchymal features of vimentin positivity and a rich distribution of matrix proteins around tumor cells. They lacked epithelial marker positivity but were faintly EMA positive. Ultrastructurally, primitive cellular junctions, desmosomes, and gap junctions were frequently seen between tumor cells. The gap junctions correlated with connexin 26 immunoreactivity. Although lacking an obvious epithelial nature, these features could be interpreted as showing an abortive differentiation mimicking meningothelial (arachnoidal) cells, which, physiologically, regulate cerebrospinal fluid between blood vessels and brain parenchyma.

Ultrastructural profile of microcystic meningioma

OBJECTIVE

Microcystic meningioma was originally classified as a subtype of meningioma by the World Health Organization classification of brain tumours in 1993, and accounts for 1.6% of intracranial meningiomas. This subtype is a variety of meningioma in which micro- and macro-cysts are diffuse. The morphologic characteristics are well defined, while the histogenetic mechanism that give rise to these patterns remain unclear.

MATERIALS AND METHODS

The authors present an electron microscopic study of an unusual case of fronto-temporal microcystic meningioma, manifesting as history of headache, right paresis and dysphasia in a 73-year-old female. Computer tomography revealed a large hypodense mass in the left fronto-temporal region, with slight contrast enhancement.

RESULTS

Ultrastructural observation showed complex alterations among small vessels and intratumoral capillaries in a background of severe modification in vessel permeability.

CONCLUSIONS

This electronic microscopy study documented that growth of the cyst was due not only to accumulation of in extracellular fluid, but also to cytolysis consequent to ingravescent hydropic degeneration.

Microcystic meningioma in a dolphin (Delphinus delphis): immunohistochemical and ultrastructural study

A wild common dolphin was found stranded on the French Atlantic coast. At necropsy, an intracranial grey- to tan-coloured mass (7 x 5 x 4 cm) was found at the right cerebellopontine angle, compressing the right cerebellar hemisphere, the brainstem and the occipital lobe of the right cerebral hemisphere. Microscopically, the tumour was composed of small lobules of polygonal to elongated neoplastic cells with multifocal areas of stellate and vacuolated cells. Neoplastic cells strongly expressed vimentin, S-100 protein and neuron-specific enolase. They were rarely positive for cytokeratin. Ultrastructurally, the neoplastic cells displayed all the diagnostic features of meningiomas and in some areas showed long cytoplasmic processes delimiting extracellular spaces. The immunohistochemical and ultrastructural features were consistent with the histopathological diagnosis of a microcystic meningioma. This is the first report of a meningioma in dolphins or in any other cetacean species.

Primary extracranial meningioma of the pelvis: a light microscopic, immunohistochemical, and ultrastructural study

BACKGROUND

Extracranial meningiomas are rare tumors which have been described in head and neck. The occurrence in mediastinum and retroperitoneum is even rarer. This presented case records a unique location, a meningioma arising in pelvis.

CASE

A 52-year-old woman presented with an ovarian mass. The histology of the resected tumor revealed sheets of bland epithelioid cells arranged in prominent whorls with psammoma bodies typical of meningothelial meningioma. Immunohistochemical analysis demonstrated diffuse strong positivity for vimentin and epithelial membrane antigen (EMA). There was moderate reactivity for cytokeratin, estrogen (ER) and progesterone (PR) receptors. By electron microscopy, the tumor cells expressed desmosomes and abundant intermediate filaments.

CONCLUSION

According to our review of literature, this is the first reported case of a primary pelvic meningioma. Its benign appearance and 4-year disease-free survival without clinical or radiological evidence of intracranial disease favors the pelvis as the primary site.

Intracerebral schwannoma clinically and radiologically mimicking meningioma

A case of intracerebral schwannoma (ICS) occurring in a 33-year-old woman is presented. The patient's history of headache, numbness, tingling and the recent development of weakness of the right upper extremity with right facial droop began during pregnancy. Magnetic resonance imaging (MRI) showed a 4 x 2 x 2 cm heterogeneous, gadolinium-enhanced mass at the left frontoparietal junction, with peritumoral edema and a dural-based attachment. During her pregnancy, the mass increased in size. The surgically resected specimen consisted of lobulated, somewhat gelatinous soft tissue. Microscopically, the tumor demonstrated classic biphasic Antoni type A and B patterns, admixed with degenerative changes. Immunohistochemically, the neoplastic cells were positive for S-100 protein (diffuse and strong), CD34 (primarily in Antoni B areas), glial fibrillary acidic protein (GFAP; weak and diffuse) and calretinin (mainly in Antoni A areas), while none was positive for CD31, estrogen and progesterone receptors, bcl-2, or epithelial membrane antigen (EMA). Ultrastructurally, basal laminae and Luse bodies were identified. The differential diagnosis includes fibrous meningioma, solitary fibrous tumor, and ICS. Twenty-seven cases of ICS were reviewed in which the histological diagnosis was confirmed immunohistochemically or ultrastructually, and the cases were summarized (including the present case). A combined use of immunostains (S-100 protein, EMA, CD34, and maybe calretinin) is of great help in distinguishing ICS from its histological mimickers.

Primary chordoid meningioma of lung

Primary meningiomas of the lung are rare. Most pulmonary meningiomas are typical syncytial or transitional meningiomas with smaller numbers of fibrous-type tumors. Herein, we report an unusual pulmonary tumor with the microscopic, immunohistochemical, and ultrastructural characteristics of a chordoid meningioma. The tumor was composed of cords and fascicles of small- to medium-sized spindle and epithelioid cells with eosinophilic cytoplasm and round nuclei with finely dispersed chromatin. The tumor cells were surrounded by an abundant mucoid, vacuolated stroma. The periphery of the tumor was enveloped by a significant lymphoplasmacytic infiltrate. The neoplastic cells were positive for vimentin and epithelial membrane antigen only. The unusual morphology of the tumor caused significant diagnostic difficulties. The differential diagnosis included inflammatory myofibroblastic tumor, spindle cell myoepithelioma, and extraskeletal myxoid chondrosarcoma. To the best of our knowledge, this is possibly the first description of an extracranial or intrapulmonary chordoid meningioma.

Meningioma with eosinophilic granular inclusions

Rare meningiomas have been described that contain eosinophilic inclusions that have a granular or granulofilamentous ultrastructure. We describe a 66-year-old woman who developed a planum sphenoidale meningioma. Histologically, the tumor was composed of meningothelial cells arranged in fascicles and whorls, typical of a well-differentiated meningioma. Many tumor cells contained round intracytoplasmic eosinophilic inclusions that were periodic acid Schiff-negative and red on Masson trichrome. The inclusions were immunopositive for vimentin, and were immunonegative for epithelial membrane antigen, smooth muscle actin, desmin and type IV collagen. Ultrastructural examination showed the inclusions were composed of round to oval, well-demarcated, non-membrane-bound, osmiophilic granular material. The inclusions within this tumor had histochemical, immunohistochemical and ultrastructural properties not described in other reported meningiomas with eosinophilic granular or granulofilamentous inclusions.

Sclerosing meningioma: immunohistochemical analysis of five cases

Sclerosing meningioma is a rare morphologic subtype of meningioma and may be mistaken for atypical or malignant meningioma and astrocytoma or schwannoma because of marked collagen deposits and a sparse population of cells with little resemblance to meningothelial cells. Authors describe the histopathologic and immunophenotypic features of five cases of sclerosing meningioma. Histologically, all the cases consisted of paucicellular collagenous tissue containing spindle cells with or without small foci of meningothelial cell proliferation. The morphology and immunohistochemical profile of the spindle cells were different from those of conventional meningothelial cells. The meningothelial cells showed a typical immunoreactivity of conventional meningiomas, while the spindle cells displayed a strong expression of vimentin. The Ki-67 labelling index was uniformly low in all cases, and none of cases expressed p53 protein. In summary, the recognition of meningothelial cells in massively sclerotic lesions is helpful for a correct diagnosis. In the cases with a total absence of meningothelial cells, however, the vague collagenous whorls are more diagnostic rather than immunohistochemistry. Considering association with clear cell meningioma, prospective and retrospective long-term follow-up is necessary for deciding whether reminiscent clear cell meningiomas should be separated from sclerosing meningioma or not.

Cytologic features of chordoid meningioma. A case report

BACKGROUND

Chordoid meningioma is a rare subtype of meningioma characterized by myxoid matrices deposited among epithelioid or vacuolated tumor cells and infiltrates of inflammatory cells, and its cytologic features have rarely been reported.

CASE

A 57-year-old man with a history of headache and visual disturbance presented with a tumor in the suprasellar region. Intraoperative touch smear cytology of the tumor disclosed a cord-like arrangement of polygonal tumor cells occasionally containing intranuclear inclusions. Furthermore, periodic acid-Schiff-positive, mucinous matrices were deposited among the tumor cells. Also, infiltrates of lymphocytes and plasma cells were noted. Histologic, immunohistochemical and ultrastructural examination confirmed the diagnosis of chordoid meningioma.

CONCLUSION

Intraoperative smear cytology in a case of chordoid meningioma showed distinctive cytologic features suggestive of the histologic patterns. The cytologic features, together with a histologic examination, are useful for its diagnosis.

Pulmonary Meningothelial-like Nodules

BACKGROUND

Minute pulmonary meningothelial-like nodules (MPMNs) are incidental interstitial pulmonary nodules. They share histologic, ultrastructural, and immunohistochemical features with meningiomas (MGs).

DESIGN

Sixteen cases yielding 33 separate MPMNs and 10 cases of benign MG were studied. Immunohistochemical studies and mutational analyses were performed on microdissected tissue using 20 polymorphic microsatellite markers targeting 11 genomic regions in an effort to identify genetic similarities of MPMN and MG.

RESULTS

A total of 96.6% of MPMNs stained positive for vimentin, 33.3% for epithelial membrane antigen, 3% for S-100, and all were negative for cytokeratin and synaptophysin. Loss of heterozygosity (LOH) was identified in 25% of single MPMN affecting 3 genomic loci. No solitary MPMN had more than 1 LOH event. Multiple LOHs were seen only in MPMN-omatosis syndrome, where 33.3% of MPMNs showed LOH affecting 7 genomic loci. MG showed the highest frequency of LOH with major events seen at 22q (60%), 14q (42.8%), and 1p (44.4%) that were not shared by MPMN.

CONCLUSION

Isolated MPMN lacks mutational damage, consistent with a reactive origin. MPMN-omatosis syndrome might represent the transition between a reactive and neoplastic proliferation. MPMNs are different from MG based on the major molecular genetic events seen in their formation and progression.

Melanocytic colonization of a meningothelial meningioma: histopathological and ultrastructural findings with immunohistochemical and genetic correlation: case report

OBJECTIVE AND IMPORTANCE

Melanocytic colonization of nonpigmented extracranial tumors has been reported in adenocarcinomas, squamous cell carcinomas, skin appendage tumors, and dermatofibrosarcoma protuberans. To our knowledge, melanocytic colonization of a meningioma has not previously been described.

CLINICAL PRESENTATION

We report an unusual case of a 70-year-old African-American woman who presented with a large frontoparietal meningioma that extended through the calvarium.

INTERVENTION

Craniotomy with gross total resection of the tumor was performed. Histochemistry, immunocytochemistry, ultrastructural analysis, and molecular genetic study via fluorescence in situ hybridization confirmed melanocytic colonization of a meningothelial meningioma.

CONCLUSION

With the inclusion of meningothelial meningioma, the spectrum of tumors affected by melanocytic colonization continues to expand.

Meningioma with extensive noncalcifying collagenous whorls and glial fibrillary acidic protein expression: new variant of meningioma diagnosed by smear preparation

The purpose of this report is to describe the unique cytological findings of a new recently characterized type of meningioma that has extensive noncalcifying collagenous whorls and glial fibrillary acid protein (GFAP) expression. This new entity, described by Haberler and colleagues, was named whorling sclerosing variant of meningioma. The patient was a 34-yr-old white man with a large tumor in the brainstem. Intraoperative smear preparations showed a tumor with a large number of solid hyaline masses in a loose background and in focal areas tumor cells formed cohesive nests with a somewhat whorling appearance. The histological sections showed a neoplasia composed of innumerable eosinophilic, collagenous, noncalcified round deposits, cuffed by scattered meningothelial tumor cells. The neoplastic cells showed diffuse cytoplasmic reactivity for EMA and vimentin, as well as positivity to GFAP. This is the first cytological description of this new entity in the literature.

Immunohistochemical and ultrastructural study of gap junction proteins connexin26 and 43 in human arachnoid villi and meningeal tumors

Human arachnoid villi and meningiomas are known to have gap junctions formed by connexin (Cx) proteins. We examined the expression and localization of Cxs in normal human arachnoid villi and meningeal tumors (meningiomas and hemangiopericytomas) by immunohistochemistry and Western blots. In arachnoid villi, strong immunopositivity for connexin26 (Cx26) and connexin43 (Cx43) was detected in the cap cell layer, cap cell cluster, and central core. They were weakly expressed in the fibrous capsule. In meningiomas they were strongly expressed in the meningotheliomatous area and weakly positive in the fibrous area. None of them were expressed in hemangiopericytomas. By immunoelectron microscopy, Cx26 and Cx43 were distributed on the cell membranes in arachnoid villi and meningiomas. In the Western blots in arachnoid villi and meningiomas, Cx26 and Cx43 were shown at bands with molecular weights of 26 kD and 42-47 kD, respectively. The degree of positivity for Cxs was different between subtypes of meningiomas. These findings suggest that expression of Cx26 and Cx43 might be related to the differentiation of the arachnoid villi and meningiomas, and exhibit the different origin of various subtypes of meningiomas. We proposed that Cx expression is one of the useful markers for the differentiation of meningioma and hemangiopericytoma.

Fine needle aspiration cytology of primary pulmonary meningioma associated with minute meningotheliallike nodules. Report of a case with histologic, immunohistochemical and ultrastructural studies

BACKGROUND

Pulmonary meningioma is an unusual tumor located in the lung. Minute pulmonary meningotheliallike nodules are also uncommon tumor-like lesions found at the pleuropulmonary level as solitary or multiple nodules. The association of both entities is described in a recent report.

CASE

A 58-year-old, male smoker without pathology underwent radiologic study before a surgical procedure. A peripheral nodule was found in the left lower lobe of the lung with benign characteristics. Fine needle aspiration cytology was performed under computed tomography guidance. Cytologic examination showed features of transitional meningioma and other lesions near the tumor. Minute pulmonary meningotheliallike nodules were also present.

CONCLUSION

A diagnosis of meningioma should be considered when there is a combination of scanty material, whorls composed of concentrically arranged cells and isolated cells with intranuclear inclusions. The simultaneous presence of meningioma and meningotheliallike nodules corroborates the unifying hypothesis of their common origin and the nature of these rare pulmonary lesions.

The relationships among ultrastructural angiogenic features, Na+ K+, Ca+2, Mg+2 ATP-ase activities and SOD concentration in the microvasculature of intracranial meningiomas and glial tumors

The purpose of this study was to investigate the relationship among ultrastructural angiogenic features, adenosine-5'-triphosphatase (ATP-ase) activities and superoxide dismutase (SOD) concentration in the microvasculature of intracranial meningiomas and glial tumors. We examined 20 tumor materials from 20 adult patients with intracranial meningioma or glial tumor who underwent selective surgery, dividing them into two groups based on the type of the tumors. Group I consisted of 10 meningioma-materials, and Group II of 10 glial tumor-materials. Na+-K+, Mg+2 and Ca+2 ATP-ase activities in Group I were significantly higher than those in Group II (p < 0.01). The SOD activity in Group I was significantly lower than that in Group II (p < 0.01). According to electron microscopic findings, vascular endothelial proliferation and ultrastructural cytoplasmic changes in the glial tumors were more prominent than those in the meningiomas. Our results show that there is a meaningful correlation among an increased endothelial proliferation, a decreased ATP-ase level and an increased SOD activity in the meningiomas and glial tumors.

Meshy meningioma: a potential novel variant

A potential novel variant of meningioma is reported. The tumor was solid, hard, white-colored, well circumscribed in a fibrous capsule and fixed to the dura, showing no invasion into the brain parenchyma. Histopathological study presented a sparsely cellular tumor composed of cells with fine reticular or mesh-like cytoplasm, each containing an oval nucleus. Mitotic figures were rarely seen. Immunohistochemical studies of tumor cells showed positive immunoreactivity for vimentin and epithelial membrane antigen but were negative for GFAP, desmin, neurofilament, keratin, S-100, CD34 and CEA. Bipolar neoplastic cells and long processes were noted on ultrastructural observation; these were attached side by side to each other by desmosomes, resulting in a mesh-like configuration. Perinuclear cytoplasm and processes were rich in intermediate filaments and rough endoplasmic reticulum. These microscopic and ultrastructural features have never before been reported among the variants of meningioma. The name 'meshy meningioma' is proposed for this novel variant.

Establishment of primary human meningiomas as subcutaneous xenografts in mice

Meningiomas are the most frequently occurring benign central nervous system tumours. We determined whether a subcutaneous animal model of meningioma was feasible by implanting fresh meningioma tissue from six patients into 60 athymic (nude) mice, either as tissue blocks (38 mice) or as cell suspensions (22 mice). The tumour take-rates were 74% (block) and 50% (suspension), and the xenografts retained the original tumour grade and subtype morphology by light microscopy. Comparison of cell proliferation markers in xenografts and original tumours gave similar immunohistochemical score rates for Ki-67, but not for PCNA. With the exception of one atypical tumour surgical specimen, all tumours lacked p53 immunopositivity. Transmission electron microscopy of sections of tumour xenografts revealed ultrastructural features, including desmosomes and desmosome-like structures, characteristic of well-differentiated meningiomas. The xenografts grew progressively with a volume increase of more than 10-fold over 6-11 months and an apparent doubling time of 16 weeks. This study demonstrates the utility of the subcutaneous meningioma xenograft as a model for further biological and therapeutic studies.

The neurofibromatosis 2 protein product merlin selectively binds F-actin but not G-actin, and stabilizes the filaments through a lateral association

The neurofibromatosis 2 protein product merlin, named for its relatedness to the ezrin, radixin and moesin (ERM) family of proteins, is a tumour suppressor whose absence results in the occurrence of multiple tumours of the nervous system, particularly schwannomas and meningiomas. Merlin's similarity to ERMs suggests that it might share functions, acting as a link between cytoskeletal components and the cell membrane. The N-terminus of merlin has strong sequence identity to the N-terminal actin-binding region of ezrin; here we describe in detail the merlin-actin interaction. Employing standard actin co-sedimentation assays, we have determined that merlin isoform 2 binds F-actin with an apparent binding constant of 3.6 microM and a stoichiometry of 1 mol of merlin per 11.5 mol of actin in filaments at saturation. Further, solid-phase binding assays reveal that merlin isoforms 1 and 2 bind actin filaments differentially, suggesting that the intramolecular interactions in isoform 1 might hinder its ability to bind actin. However, merlin does not bind G-actin. Studies of actin filament dynamics show that merlin slows filament disassembly with no influence on the assembly rate, indicating that merlin binds along actin filament lengths. This conclusion is supported by electron microscopy, which demonstrates that merlin binds periodically along cytoskeletal actin filaments. Comparison of these findings with those reported for ERM proteins reveal a distinct role for merlin in actin filament dynamics.

Chordoid meningioma

Chordoid meningioma is a relatively rare variant that is often associated with peritumoral lymphoplasmacellular infiltration causing Castleman syndrome (CS). We present a 44-year-old woman with chordoid meningioma not associated with CS. The patient presented with epilepsy and right hemiparesis (Todd's palsy) on admission. The radiological findings revealed an extraaxial mass lesion in the premotor cortex. They were compatible with a preoperative diagnosis of meningioma. No physical abnormalities related to CS were detected. A left frontal craniotomy was performed. The tumor surface was gelatinous, and it was totally resected with the attached dura mater (Simpson grade I). The patient had an uneventful recovery, and her seizures subsided. The pathological findings of the specimens revealed nests and cords of spindle and epithelioid cells with abundant myxoid matrix, mimicking the features of chordoma. On the basis of radiological, immunohistochemical, and electron microscopic findings, chordoid meningioma was verified, and a review of the literature was performed.

Brain oedema in secretory meningiomas

Brain oedema is usually associated with intracranial meningiomas in about 50-66%. As underlying causes, different factors like localisation, vascular supply, angiogenic growth factors and histological subtypes are discussed, and its existence is probably multifactorial. We present 11 patients with the rare subtype of secretory meningiomas. Brain oedema was observed in 82%. These tumours are localised mainly at the frontal convexity and at the sphenoid ridge. All 11 patients were female so that hormonal factors also may play a role in the production of peritumoural oedema. The postoperative outcome was good and no recurrences were seen during follow-up.

Ultrastructural examination is essential for diagnosis of papillary meningioma

AIMS

Papillary meningioma is a rare meningeal tumour. To date only a few cases have been reported and their immunohistochemical features have not been fully documented.

METHODS AND RESULTS

A 49-year-old woman presented with a 2-month history of headaches and memory disturbance. CT and MRI imaging showed an enhancing pineal mass with extension into the occipital lobes and invasion of the splenium. At surgery, the tumour was found to be tough and vascular with a well-defined capsule. No recurrence was noted 19 months after the operation. In another case a 44-year-old woman was admitted with 1-month history of headaches, poor memory, imbalance and diplopia. CT scan showed a large hyperdense, uniformly, enhancing mass within the middle cranial fossa at the petrous ridge. The tumour recurred 19 and 25 months after first resection. The histology of both tumours was similar. The neoplasms contained polygonal cells with a moderate amount of cytoplasm, rounded regular nuclei and distinct cell borders. The cells were arranged radially around the blood vessels (perivascular pattern) and a papillary pattern was seen only focally. Mitotic figures were moderately frequent. Immunohistochemistry showed that both tumours were immunoreactive to vimentin and NSE, whereas GFAP, CAM5.2, EMA, S100 protein and synaptophysin were negative. Electron microscopy revealed interdigitating cell processes, desmosomes and intermediate filaments.

CONCLUSIONS

The histological and immunohistochemical features of these two tumours are complex and difficult to interpret. Although papillary meningiomas were considered in our initial differential diagnosis, the final conclusion was possible only when the ultrastructural features were revealed.

Xanthomatous changes in atypical and anaplastic meningiomas. Light and electron microscopic investigations

Xanthomatous changes may occur in meningiomas of different histological type, however their incidence in combination with histological features of atypical or anaplastic meningioma has not been previously documented. In this report we present clinicopathologic, immunohistochemical and ultrastructural studies in the surgical cases of two atypical and three anaplastic meningiomas exhibiting prominent xanthomatous changes. In all tumors the xanthomatous cells were seen in association with typical meningioma structures such as meningothelial whorls or psammoma bodies as well as within the tumor parts displaying pleomorphism, patternless growth, increased cellularity, presence of necroses and mitoses or brain invasion. Ultrastructural study revealed a wide-range of lipid-containing cells, reflecting a continuum of gradual transition between polymorphic meningioma cells and xanthomatous cells. Commonly, the lipidized cells exhibited different degrees of plasmalemmal interdigitations and desmosomal junctions. Our study allowed us to confirm the meningothelial origin of xanthomatous cells in atypical and anaplastic meningiomas. Moreover, the ultrastructural observations of lysosomes in the majority of xanthomatous cells and the immunoreactivity for the CD68 antigen indicated their macrophage characteristics. It seems that a mixed meningeal/macrophage nature of xanthomatous cells can be related to the functional and structural multipotentiality of the primary leptomeningeal cells.

[Contribution of immunohistochemistry and electron microscopy for the diagnosis of meningeal hemangiopericytomas. 15 case reports]

Meningeal hemangiopericytomas (HPC) are rare CNS tumors with a pour prognosis compared to meningiomas. In order to define diagnosis criteria, we performed an immunohistochemical and ultrastructural study in respectively 15 and 5 meningeal HPC. The following antibodies anti-KL1, EMA, vimentin, CD34, factor VIII, alpha-smooth actin, estrogen and progesteron receptors (RE, RP) were used in paraffin embedded sections whereas anti-NCAM and E-cadherin antibodies were used on frozen sections when available. We can differentiate meningeal HPC from meningioma because of a complete lack of immunostaining with epithelial markers as well as with NCAM antibody or RE and RP receptors. Besides a positivity with CD34 and alpha-smooth actin antibodies was always observed even focally in HPC. On the other hand, solitary fibrous tumor showed a strong and diffuse positivity with anti CD34 and anti-vimentin antibodies. Electron microscopy can be helpful in some instances showing membrane basal-like substance and absence of desmosomes.

Primary meningeal sarcomas with leiomyoblastic differentiation: a proposal for a new subtype of primary meningeal sarcomas

Two cases of primary meningeal sarcoma with leiomyoblastic differentiation are presented. In case no. 1, the tumor showed anaplastic spindle cell tumor components intermingled with anaplastic meningothelial components. Meningothelial tumor cells gradually became transformed into spindle tumor cells. Spindle tumor cells reacted with antisera to muscle actin (HHF-35) and alpha-smooth muscle actin. However, unchanged meningothelial tumor cells did not react with the antisera to HHF-35 and alpha-smooth muscle actin. Electron microscopy showed condensations of cytoplasmic fibers and pinocytotic vesicles in spindle tumor cells similar to those seen in smooth muscle cells. In case no. 2, the tumor cells consisted predominantly of sheets of round or polygonal cells as seen in an epithelioid leiomyosarcoma. The neoplastic cells had frequent nuclear inclusions, such as those seen in meningiomas. Immunohistochemically, the tumor cells reacted with antisera to desmin and to HHF-35. Electron microscopy showed a basal lamina around the cytoplasm of tumor cells. Intranuclear inclusions with various cytoplasmic organelles were frequently observed in the tumor cells, as in meningiomas. Interdigitating cytoplasmic processes and intercellular junctional complexes, however, were not found in the tumor cells. Two possible hypotheses explain the occurrence of leiomyoblastic characteristics of these cases. In case no. 1, leiomyoblastic cells originated from meningothelial cells with the advancement of meningothelial anaplasia. In case no. 2, pluripotential mesenchymal cells in the meninges differentiated into meningothelial and smooth-muscle cell lines at the time of tumor growth. With consideration of previous publications on primary meningeal sarcoma, these cases are the first reported primary meningeal sarcoma with leiomyoblastic and meningothelial differentiation.

Primary extracranial meningioma of the foot: a case report

We present a rare case of primary extracranial meningioma in a 36-year-old man, who had a solitary multinodular mass located in the plantar muscle of the foot. The histology of specimens from simple excision was typical of meningioma, showing bland spindle cell proliferation with a whorl pattern. Immunohistochemical analysis demonstrated that the tumor cells showed diffuse and strong positivity for epithelial membrane antigen as well as moderate reactivity for cytokeratin and vimentin. Ultrastructurally, the tumor cells were characterized by thin bipolar cytoplasmic processes and joined by multiple small desmosomes. There were frequent pinocytotic vesicles and a distinct external lamina on the cell surface. These findings suggest that this primary ectopic meningioma, arising in the soft tissue, may have been derived from perineurial cells of the peripheral nerve, but was morphologically distinguishable from perineurioma. Primary extracranial meningioma should be included in the differential diagnosis of soft-tissue spindle cell tumors, especially those of peripheral nerve origin.

Meningioma with granulofilamentous inclusions

The authors report a case of intracranial meningioma with granulofilamentous inclusions. A 50-year-old man had right trigeminal neuralgia due to trigeminal nerve compression by a petroclival tumor and received tumor resection. Microscopically, tumor cells containing eccentric nuclei and intracytoplasmic hyaline inclusions were arranged in sheets and whorls. The inclusions were negative for periodic acid-Schiff reaction. No histological anaplasia was seen. Immunohistochemistry showed epithelial membrane antigen reactivity on the cytoplasmic membrane. Immunoreactivity for vimentin was recognized in cytoplasm adjacent to inclusions. However, confocal laser microscopic study revealed immunoreactivity for vimentin even inside some inclusions. Ultrastructurally, interdigitation of cytoplasmic processes and desmosomes connecting adjacent cells were noted. Inclusions were composed of numerous fine osmiophilic granules attached by intermediates filaments. These findings were consistent with a meningioma with the granulofilamentous inclusions described earlier. The findings demonstrated by confocal laser microscopy and electron microscopy suggest that these granular materials may be the metabolic products of vimentin filaments.

Meningioma presenting as an intraoral mass in a patient with neurofibromatosis type 1

A 77-year-old woman with neurofibromatosis type 1 presented with ill-fitting dentures due to intraoral extension of a right temporal fossa mass. Computed tomographic scanning demonstrated that the masticator space mass bowed the zygomatic arch and remodeled the lateral orbit and maxillary sinus walls, findings that were consistent with the clinical diagnosis of a neurofibroma with possible malignant transformation. However, light microscopic, immunohistochemical, and ultrastructural examination of tissue from an incisional biopsy specimen were diagnostic of meningioma. This case illustrates that the clinicopathologic differential diagnosis of an enlarging mass in patient with neurofibromatosis should include sporadic, unrelated neoplasms as well as tumors known to be associated with the syndrome.

Malignant meningioma with rhabdoid transformation

We report a rare case of recurrent meningioma with malignant change and rhabdoid transformation in a 54-year-old woman who presented with severe headache and progressive weakness of the right extremities. The patient had a history of atypical meningioma and had undergone a craniotomy to remove a tumor nine years earlier. We discuss the distinctive morphologic, immunohistochemical staining and ultrastructural features of a recurrent malignant meningioma. A meningioma with rhabdoid transformation may indicate aggressive biologic and clinical behavior of the tumor.

[Lipomatous meningioma: report of two cases and review of the literature]

Lipomatous meningioma is a benign tumor characterized either by an admixture of mature adipocytes and meningioma or the production of triglycerides by neoplastic meningothelial cells assuming a lipoblast-like appearance. The authors report on two instances of this exceedingly rare lesion occurring in the left middle cranial fossa and over the right frontal convexity of two female patients aged 79 years and 60 years, respectively. In the former, the tumor was an incidental autopsy finding, while the latter underwent surgery for symptoms of intracranial space occupation. Light microscopy showed interwoven islands of fatty tissue and transitional meningioma in the first case; whereas a monomorphous signet-ring cell phenotype prevailed in the second. Oil-Red-O staining confirmed the presence of neutral fat in both specimens. Immunohistochemical coexpression of epithelial membrane antigen, vimentin, and S100 protein supported the meningothelial origin of tumor cells. On the other hand, the CD 68 macrophage antigen was not detected. Cytoplasmic lipid droplets along with hallmarks of meningothelial differentiation were visualized ultrastructurally in part of the meningioma component of the first case and throughout the second. These findings are consistent with a metaplastic origin of the adipocytic element. Whatever its histogenesis, lipomatous meningioma may, on occasion, represent a major challenge with therapeutic implications for both preoperative imaging and histological diagnosis.

[Rhabdoid meningioma: a potentially aggressive new variant]

Rhabdoid meningioma is a recently recognized clinicopathologic entity characterized histologically by cytoplasmic aggregates of intermediate filaments, and clinically by the propensity of such tumors to pursue an aggressive course. The authors report on clinical, radiologic and pathologic findings in three cases of rhabdoid meningioma identified in a retrospective surgical series of 204 meningothelial tumors. Patients included two females, aged 39 and 55 years, and a 54-year-old male. In the first two cases the tumors were located on the right and left lesser sphenoid wing, respectively; in the third case, the right cerebellopontine angle was affected. All three neoplasms evolved on a background on transitional meningioma and were conspicuous for dis-cohesive tumor cells and suppression of syncytical architecture. Immunohistochemistry and ultrastructural examination confirmed the meningothelial origin of inclusion-bearing rhabdoid cells. Although none of the tumors showed evidence of histologic anaplasia and Ki-67 labeling indices remained inferior to 2%, infiltrative growth into adjacent brain was noted in all three cases. On follow-up ranging from 8 months to 6 years, the patients remained either disease-free or alive with nonprogressive residual tumor. On account of their clinical behavior, well-differentiated rhabdoid meningiomas will be accommodated in the category of atypical meningiomas (WHO grade II). Their pathogenesis is likely to involve disrupted cytoskeletal integration of cell motility and proliferation, of which the rhabdoid phenotype may possibly represent a morphologic correlate.

Charging phenomena in PEEM imaging and spectroscopy

Spectromicroscopy with the imaging technique of X-ray photoelectron emission microscopy (X-PEEM) is a microchemical analytical tool installed in many synchrotron radiation laboratories, and which is finding application in diverse fields of research. The method of sample analysis, X-ray absorption spectroscopy, does not encounter the same problems as X-ray photoemission spectroscopy when sample charging occurs, hence even good insulators may often be analyzed without any apparent artifacts in images or spectra. We show, however, that charging effects cannot be neglected. We model the effect of surface charge formation on the secondary electron yield from uniform samples to demonstrate that surface charge primarily reduces the yield of electrons which may contribute to the detected signal. We illustrate that on non-uniform insulating samples, localized centers of charge may substantially affect microscope imaging and resolution as the electrostatic field close to the surface is distorted. Finally, in certain circumstances non-uniform surface charge may lead to unexpected lineshapes in X-ray absorption spectra causing, in some extreme cases, negative spectra. These negative spectra are explained, and several strategies are reviewed to minimize the impact of sample charging when analyzing poorly conducting samples of any nature.

Fibrous meningioma with tyrosine-rich crystals

A 58-year-old African-American woman presented with a 6-month history of headaches. A magnetic resonance imaging scan of the head revealed a 5-cm, enhancing dura-based mass in the left parietal region. The variably cellular tumor was composed of uniform spindle cells associated with intercellular collagen and numerous radially arranged "petal-shaped" clusters of eosinophilic crystals. The tumor was diagnosed by light microscopy as a fibrous meningioma. Ultrastructural examination disclosed cells with complex interdigitating processes connected by desmosome-like cell junctions, abundant intercellular collagen fibers, and prominent, densely osmiophilic crystals featuring radiating teardrop shaped petals emanating from a central core. A positive Millon reaction showed these crystals to consist at least in part of tyrosine. By morphology, histochemistry, and ultrastructure, the crystals resembled tyrosine-rich crystals occurring in salivary gland tumors. This is the first report of a fibrous meningioma containing tyrosine-rich crystals.

Acoustic neuromas and meningiomas. Histopathological aspect: a post mortem study on temporal bones

The histopathological changes in the temporal bones of three deceased donors individuals, two with concomitant acoustic tumors and one with concomitant petroclival meningioma have been studied. The differences between neuromas and meningiomas are examined. The different clinical relevance and the different therapeutic guidelines are discussed.

Cerebellar papillary meningioma in a 3-year-old boy: the usefulness of electron microscopy for diagnosis

We report one case of papillary meningioma located in the posterior fossa in a 3-year-old boy. Despite a gross total resection, a major recurrence occurred 6 months later that was operated on. Eight months later, another recurrence was observed with intracranial metastases and dissemination throughout the cerebrospinal fluid. The tumor had a papillary architecture more obvious in the recurrence. Areas of necrosis were numerous. Tumor cells had large clear atypical nuclei. Many mitotic figures were seen and Ki-67 labeling index was high. The tumor cells were immunoreactive for vimentin and polysialylated neural cell adhesion molecule only, ruling out a diagnosis of ependymoma or medulloblastoma. Diagnosis of meningioma was done by electron microscopy, which showed interdigitating cytoplasmic processes and cell junctions. Cytogenetic study revealed unusual karyotypic abnormalities.

Clinical application of three-dimensional anisotropy contrast magnetic resonance axonography. Technical note

The utility of three-dimensional anisotropy contrast (3DAC) magnetic resonance (MR) axonography, a method sensitive to neuronal fibers and their directionality, was investigated in the clinical setting using a 3-tesla MR imaging system based on a General Electric Signa platform. The study focused on healthy volunteers and patients with common structural central nervous system disorders, namely chronic infarction, brainstem cavernous hemangioma, supratentorial meningioma, and astrocytoma. Three orthogonal anisotropic diffusion-weighted images were first obtained. Three primary colors were each assigned to a diffusion-weighted image, respectively, and the images were subsequently combined into a single-color image in full-color spectrum (3DAC MR axonography image). Fiber-tract definition in the cerebral peduncle of the midbrain of healthy volunteers showed intersubject variation, with two general patterns recognized: dispersed (60% of cases) and compact (40% of cases). Pathological alterations in the fiber tracts were readily identified in cases involving wallerian degeneration of the pyramidal tract, as illustrated in the cases of chronic infarction. Displacement of major tracts, such as the medial lemniscus or corticospinal tract, as well as fiber directionality, was also easily recognized in cases of mass lesions. As an imaging method uniquely capable of providing information regarding axonal connectivity, 3DAC MR axonography appears to have promising potential for routine clinical application.

Clear cell meningioma of the lumbo-sacral spine with chordoid features

Clear cell meningioma (CCM) is a peculiar variant that differs from conventional meningioma in affecting younger patients, arising more often in spinal or cerebellopontine locations, and showing a higher recurrence rate. Classical meningothelial areas are scarce in these tumors and the differential diagnosis with other neoplasms, particularly metastatic carcinoma, is often difficult. We report a case of clear cell meningioma from the lumbosacral spine in which location, radiologic presentation, light microscopic appearance in initial sampling, and some of the ultrastructural findings were reminiscent of chordoma. The tumor cells were diffusely positive for vimentin and very focally positive for epithelial membrane antigen. Ultrastructural demonstration of interdigitating cell processes joined by numerous desmosomes confirmed the diagnosis of CCM.

Expression of somatostatin receptor subtypes in human brain tumors

Expression of mRNA for the 5 somatostatin receptors (sst1-5) was characterized by Northern blot and RT-PCR analysis in 20 meningioma and 9 glioma samples. sst1 mRNA was detectable by Northern blots of poly-A+ RNA in meningiomas but not gliomas. In contrast, sst2 mRNA was readily detected by Northern blots of total RNA as a major 2.3 kb transcript and 2 minor 4.3 kb and 8 kb transcripts in all meningiomas and 6 out of 9 gliomas. Quantitation of the 2.3 kb sst2 mRNA showed that 15 out of 20 tumors expressed 1.3- to 33-fold higher levels than control normal human brain. Mean sst2 mRNA for the 20 meningioma samples was 978% that of normal brain. Three gliomas showed 7- to 14-fold higher sst2 mRNA than normal brain whereas the remaining samples displayed very low or undetectable levels. Immunocytochemistry of meningioma and glioma samples, with a sst2-specific antibody revealed immunoreactivity in tumor cells and peritumoral tissue, with prominent expression in blood vessels. mRNA for sst3,4,5 could not be detected by Northern blots in any of the tumors. RT-PCR analysis of meningiomas and gliomas revealed the following percent of tumors positive for a given sst mRNA: sst1 (86%), sst2 (100%), sst3 (60%), sst4 (58%), and sst5 (67%); 85% of tumors expressed 3 of the 5 subtypes. No correlation was found between the pattern of expression of sst mRNA and tumor type, location, and histology for either the meningiomas or gliomas. Our results show that meningiomas and gliomas are all positive for at least one sst subtype, the majority expressing multiple subtypes. sst2 is the most abundant isoform with a rich expression in both tumor and peritumoral tissue especially blood vessels.

Clear cell meningioma variant and clinical aggressiveness

The few reports about clear cell meningiomas (CCM) point to an inordinate clinical aggressiveness despite their histological benignity. We studied 5 CCM aiming to assess their clinicopathological, cytometric, and ultrastructural features. Two patients were females and 3 males, with a mean age of 36 years. Two tumors were spinal, one of the cerebral convexity, one of the tentorium-clinoid region, and one of the base of the skull. The first 3 were totally removed and have not recurred for a mean follow-up time of 40 months. The tentorium-clinoid and the skull base tumors had radical subtotal and partial resections, and recurred after 16 and 1.5 months, respectively. All tumors but one, a non-recurrent one, presented no signs of histological anaplasia. The proliferative capacity, as assessed by MIB-1 staining index (SI), of recurrent tumors was slightly higher than that of those tumors that did not recur. All cases showed DNA diploid pattern. Amianthoid-type fibers were disclosed on ultrastructural study. CCM arose in patients younger than those with other variants of meningioma, the spinal canal and the posterior fossa were the common sites. Finally, intracranial tumors were linked to an aggressive behavior.

Solitary fibrous tumor of the meninges

The clinical, radiologic, and pathologic features of a case of solitary fibrous tumor of the meninges at the base of the brain are reported. The tumor caused clinical symptoms in a 42-year-old Caucasian male which were indicative of compression of hypothalamus, basal ganglia, and third ventricle. Radiologically it was a large extra-axial mass isointense to brain parenchyma on precontrast T1-weighted images that filled the suprasellar cistern and deformed the left cerebral peduncle. At surgery, the tumor was firm to hard and attached to dura. Histologically the tumor was composed of spindle-cell proliferation in a collagen-rich background but exhibited regional variations. CD34 immunoreactivity was a prominent histologic finding. Ultrastructural features of meningioma, such as complex interdigitation of cell processes and intercellular specialized junctions were absent. The cells showed the typical appearances of fibroblasts with proximity of banded collagen and precollagen and cytoplasmic rough-surfaced endoplasmic reticulum. DNA ploidy analysis showed diploid DNA content. Awareness of this neoplasm may lead to increasingly frequent recognition and the current WHO classification of brain neoplasms should be modified to include this new entity.